P.W. Botha, 90, the unapologetic leader of apartheid-era South Africa who led his country into deepening political crisis and racial violence as head of state from 1978 to 1989, died Oct. 31 at his home in Wilderness, a southern coastal town. No cause of death was reported.

"Peevee" Botha was the bald, bespectacled mandarin of the ultra-right Nationalist Party. His trademark was a finger-wagging belligerence that earned him the nickname the "Groot Krokodil," or great crocodile, in Afrikaans, the Dutch language that was his native tongue.

He held a variety of portfolios before becoming defense minister in 1966. During the next decade, he engineered massive increases in the military budget to minimize the effects of the international arms embargo against the apartheid government.

He also saw the militarization of his country as a way to safeguard South Africa from foreign invasion and internal subversion. To international derision, he undertook incursions into Angola and South West Africa (later renamed Namibia) to end leftist guerrilla uprisings and what he called the "forces of chaos, communism and socialism."

As prime minister and then state president, he veered wildly between upholding and reforming apartheid, the system of racial segregation that his party initiated after coming to power in 1948. He understood its inevitable decline amid uncontrollable protests but was unwilling to appear weak to his followers.

Years after he left office and a new, black-led leadership emerged, Mr. Botha remained defiant during investigations into his regime's hard-line racial policies that led to killings, tortures and disappearances. On a technicality, he successfully evaded testifying before South Africa's Truth and Reconciliation Commission, formed to probe apartheid-era crimes.

"I did not authorize murders," he said to reporters at the time. "I will not ask forgiveness for fighting the Marxist revolutionary onslaught."

Pieter Willem Botha was born Jan. 12, 1916, at his family's farm in the Paul Roux district of the Orange Free State. The area was deeply conservative and populated largely by Afrikaners, the white descendants of 17th-century settlers who were mostly Dutch.

In his teens, Mr. Botha became a member of the National Party, then a minority political group. During the Depression, he abandoned his law school studies at the University of the Orange Free State and began his mentorship under the Nationalist leader D.F. Malan. Mr. Botha was a political organizer, a job that sometimes required thuggery and other forms of intimidation.

During World War II, he helped form the Cape branch of the Ossewabrandwag, or Ox-Wagon Fire Guard, a pro-Nazi paramilitary group that opposed his country's support for the British and other Allied powers. His involvement ended when he was threatened with internment.

In 1948, his party won the general election in a surge of Afrikaner nationalism, and Mr. Botha was elected to the lower house of Parliament.

During his first decade in office, he became his party's chief secretary. Under prime minister H.F. Verwoerd, he was minister of colored affairs; minister of community development and housing; and minister of public works.